1. Technical Field
The present invention relates to a semiconductor device including a diffusion barrier film formed over an insulating film and a conductive pattern, and a method of manufacturing the same.
2. Related Art
In recent years, copper has been used as interconnect material for semiconductor devices. Copper interconnect is formed in the form of being buried in an insulating film.
When copper is used as interconnect material for semiconductor devices, a diffusion barrier film is required to be formed over the copper interconnect in order to prevent the copper from being diffused to an upper layer of the copper interconnect. When the diffusion barrier film is formed over the copper interconnect, it is necessary to secure adhesion between the copper interconnect and the diffusion barrier film and adhesion between the insulating film in which the copper interconnect is buried and the diffusion barrier film.
Japanese Laid-open patent publication NO. 2002-203899 discloses a technique for exposing a copper layer to reducing plasma and carbon-containing plasma before forming an inorganic barrier film over the copper layer in order to improve adhesion between the inorganic barrier film and the copper layer.
With miniaturization of semiconductor devices, there is a need to reduce inter-interconnect capacitance. Lowering of a relative permittivity of an insulating film in which an interconnect is buried is effective in reducing the inter-interconnect capacitance. An example of the insulating film having a low relative permittivity may include an SiOH film, an SiCOH film or an organic polymer film. The present inventor has recognized as follows. A process of burying a conductive pattern such as a copper pattern or the like in the insulating film includes a chemical mechanical polishing (CMP) process. In the CMP process, since the conductive pattern is physically polished while being oxidized, an oxide layer is left on a surface layer of the conductive pattern after the CMP process. This residual oxide layer deteriorates an electro-migration characteristic of the conductive pattern. In addition, when an SiOH film, an SiCOH film or an organic polymer film is used as the insulating film, a surface layer of the insulating film is oxidized in the CMP process and its relative permittivity is raised.
It may be contemplated that a surface layer of the copper pattern is exposed to a reducing atmosphere as a method of eliminating the oxide layer on the surface layer of the conductive pattern. However, the present inventor has studied this method and has found that this method exposes a surface layer of the insulating film to the reducing atmosphere, thereby further raising the relative permittivity of the surface layer of the insulating film.
Another finding of the studies of the present inventor is that, when the relative permittivity of the surface layer of the insulating film is raised, it was revealed that the relative permittivity of the surface layer of the insulating film is lowered if the surface layer of the insulating film is treated by plasma of carbon-containing gas. However, it was also revealed that adhesion between the insulating film and a diffusion barrier film is lowered if the surface layer of the insulating film is treated by carbon-containing plasma.
In this manner, when the SiOH, SiCOH or organic polymer is used as the insulating film, it is difficult to prevent the oxide layer from being left on the surface layer of the conductive pattern, prevent the relative permittivity of the surface layer of the insulating film from being raised, and prevent the adhesion between the insulating film and the diffusion barrier film from being lowered.